Multiphysics thermal design of a high-speed permanent-magnet machine

In the paper, different methods for thermal design of a high-speed permanent-magnet machine are presented. The first implemented method is a numerical-multiphysics method which couples computational fluid dynamics and heat-transfer equations. The geometry of the machine in this method is considered to be 2D axi-symmetric. This method gives simultaneous solutions for the turbulent properties of the cooling fluid as well as for the temperature rise in the fluid and solid domains of the machine, but it is primarily intended for solving the fluid domain. The distribution of the temperature rise in the solid domain of the machine is estimated with a 3D numerical heat-transfer method that is the second one implemented in this paper. This method uses the properties of the turbulent flow from the 2D multiphysics method such as the temperature rise of the fluid and the coefficients of thermal convection and implements them as boundary conditions. Validation of the aforementioned methods is done using the traditional thermal-network method that is based on analytical and empirical equations and this is the third method implemented in this paper. The comparison of the results between the different methods shows a very good agreement.